Anthropogenic and Climatic Controls on Groundwater Availability in Iran

Abstract:

Groundwater is a key freshwater resource globally, in particular in arid and semi-arid regions, like Iran that has experienced one of the highest country-wide depletion rates in recent years. The objective of this study is to quantify the total amount and annual variability of groundwater loss in Iran and to determine its underlying climatic and/or anthropogenic causes. Analysis of groundwater availability is based on water level monitoring in more than 11,000 wells located in 487 sub-basins across the country. The impact of climate variability and change on groundwater storage variations is assessed using ground-based precipitation and pan evapotranspiration observations (~ 5700 stations). Quantifying anthropogenic influences on groundwater budget is based on human water withdrawal (H_out) at the sub-basin scale. Results show that groundwater depleted ∼74 km³ in Iran during 2002-2015 with highly localized and variable depletion rates at the basin and sub-basin scales. Our results show that the compound impacts of drought along with anthropogenic activities (e.g., population and agricultural growths) have caused massive groundwater depletion in Iran. While net inflows to groundwater reserves declines greatly during drought years, human withdrawals strongly dominate the effects of climate variability and change. We argue that continuation of unsustainable groundwater management in Iran can lead to significant and potentially irreversible impacts and affect a large proportion of the country’s population.